Standalone interbody implants

ABSTRACT

Stand-alone interbody fusion devices for engagement between adjacent vertebrae. The stand-alone interbody fusion devices may include frames and one or more endplates coupled to the frame. The frame may be configured and designed to provide the apertures which are designed to retain bone fasteners, such as screws or anchors, and secure the implant to the adjacent vertebrae.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 14/556,345, filed Dec. 1, 2014, which is a continuation-in-partof U.S. patent application Ser. No. 14/278,898 filed on May 15, 2014,the entire disclosures of which are incorporated herein by reference intheir entireties for all purposes.

FIELD OF THE INVENTION

The present disclosure generally relates to fixation devices forpositioning and immobilizing adjacent vertebral bodies. In particular,the devices may include stand-alone interbody fusion devices.

BACKGROUND OF THE INVENTION

As people age, the intervertebral discs in the spinal column may startto deteriorate. Subsequently, the intervertebral discs being to loseheight. As a result of the loss of height between vertebral bodies, thenerves exiting from the spinal canal become compressed and pinched,which causes pain among other neurological deficits. One solution is toinsert a spacer in place of the disc to restore the height and topromote fusion between adjacent vertebral bodies to permanently maintainthe height restoration. Additional fixation is also needed to stabilizethe spinal segment. A plate is usually provided, and the plate may bepositioned on the anterior portions of the adjacent vertebral bodies. Insome cases, the profile of the plate becomes obstructive to the anatomy.The approach to the spine is also significant in that a direct anteriorapproach requires navigation or dissection of vascular anatomy.

As a result, there is a need to provide a spacer having fixationelements to attach the spacer directly to adjacent vertebrae, to limitany profile protruding out of the spine column anteriorly, and to avoidproximal anatomy from a direct anterior approach. The spacer alone,however, may not be strong enough to support fixation elements, such asscrews, when the spacer is made solely from certain non-metallicmaterials, such as, polyether ether ketone (PEEK). Thus, there is also aneed for frames or spacers at least partially constructed of strongmaterials or in such a manner so as to provide additional support forthe fixation elements.

SUMMARY OF THE INVENTION

To meet this and other needs, stand-alone interbody fusion implants anddevices are provided. The implants may be provided with a spacer and atleast one insert or member. The implants may also be composed of a framewith one or more endplates affixed thereto. The inserts, members, orframes may be especially suited for defining apertures designed tosecure fixation elements or fasteners, such as screws, staples, pins,nails, anchors, or the like, and the spacers to adjacent vertebrae.These implants provide for a spine stabilization system that promotesfusion of adjacent vertebrae while at the same time providingstabilization of the spinal area where fusion occurs.

According to one embodiment, an intervertebral implant for implantationin an intervertebral space between adjacent vertebrae includes a spacerand at least one insert. The spacer has a superior surface, an inferiorsurface, a proximal end, and a distal end. The superior surface and theinferior surface each have a contact area configured to engage adjacentvertebrae. The spacer defines an opening extending from the superiorsurface to the inferior surface of the spacer. The opening may beconfigured for receiving bone graft material to promote fusion of theadjacent vertebral bodies. The spacer defines one or more cutoutextending from the proximal end to the opening. The spacer may alsoinclude a plurality of protrusions on the contact areas of the superiorand inferior surfaces for engaging the adjacent vertebrae.

The insert at least partially defines a fastener aperture. Theseapertures may be in the form of through holes designed, sized, anddimensioned to accommodate and receive fixation devices or fasteners,such as bone screws or anchors. The insert is coupled to the spacer suchthat at least a portion of the insert is received in the cutout in thespacer.

The insert may be configured in such a way to enhance the strength andstability of the spacer. The insert may extend a distance beyond thesuperior surface, the inferior surface, or both surfaces of the spacer(e.g., a portion of the insert may extend above or below the superiorand inferior surfaces of the spacer). For example, a front surface ofthe insert may include at least one eyebrow where the eyebrow projectspast the superior surface, the inferior surface, or both surfaces of thespacer. The fastener aperture for receiving the fastener may traversethe front surface of the insert at an angle divergent to a horizontalplane in order to help secure the implant to one or both of the adjacentvertebrae.

Unlike a traditional plate, which is typically a thin, flat sheet orstrip of material, the insert is provided with a given depth anddimension designed to integrate seamlessly with the spacer. Inparticular, the depth of the insert may be greater than the width and/orheight of the insert. The insert may include a head portion and at leastone arm projecting therefrom. The head portion may be enlarged to definethe aperture configured for retaining the fastener. The arm may extendlaterally, medially, and/or posteriorly away from the head portion. Inparticular, the arm may extend posteriorly and may be configured tomimic the shape and design of the spacer. The spacer may define at leastone recess sized and dimensioned to retain at least a portion of thearm. For example, the arm may rest against a portion of the spacer or arecess therein to form a lap joint, half lap joint, stepped joint, orthe like. Any type of joint formed between the insert and the spacer maybe secured with one or more pins.

According to another embodiment, the insert may be provided in the shapeof a ring, cylinder, c-shape, or the like. The ring or c-shaped insertmay be provided with one or more slits, for example, to allow the insertto tightly mate with the cutout through the spacer and secure the insertto the spacer. In particular, one or more slits may be longitudinallypositioned around a periphery of the ring or c-shaped insert.

According to yet another embodiment, a stand-alone implant forimplantation in a treated area of an intervertebral space betweenvertebral bodies of a spine includes a spacer and at least one member.The spacer has a first spacer portion and a second spacer portion, eachof the first and second spacer portions having a first end and a secondend. The second end of the first spacer portion is coupled to the firstend of the second spacer portion. The first and second spacer portionsform a superior surface and an inferior surface, and the superiorsurface and the inferior surface each have a contact area configured toengage adjacent vertebrae.

The member has an upper surface, a lower surface, a first lateralportion, a second lateral portion, and at least one hole traversing themember for receiving a fastener. The member is coupled to the spacersuch that the first end of the first spacer portion engages the firstlateral portion of the member and the second end of the second spacerportion engages the second lateral portion of the member.

The first and second spacer portions may be joined together in anysuitable manner. For example, the first and second spacer portions maybe mated together by a splice joint, scarf joint, butt joint, or thelike. In the alternative or in addition, the first and second spacerportions may be secured together with one or more connectors. Forexample, the connector may include at least first and second tenonssized and configured to be received within a first mortise in the secondend of the first spacer portion and a second mortise in the first end ofthe second spacer portion. Any type of joint formed between the firstand second spacer portions may be further secured with one or more pinsor the like.

The spacer portions and the member may also be joined together in anysuitable manner. Similar to the insert configuration, the member mayrest against a portion of the spacer portions or a recess therein toform a lap joint, half lap joint, stepped joint, or the like. Forexample, the member may include a first extension extending from thefirst lateral portion and a second extension extending from the secondlateral portion. The first extension may contact a first ledge on thefirst spacer portion to form a first half lap joint, and the secondextension may contact a second ledge on the second spacer portion toform a second half lap joint. If desired, the first and second half lapjoints may each be further secured with at least one pin.

According to a further embodiment, an implant for implantation in anintervertebral space between adjacent vertebrae includes a spacer and ananterior portion. The spacer has a superior surface, an inferiorsurface, a proximal end, and a distal end, for example, configured forinsertion into the intervertebral space. The superior surface and theinferior surface each have a contact area configured to engage adjacentvertebrae. The spacer defines an opening extending from the superiorsurface to the inferior surface of the spacer.

The anterior portion extends from the proximal end of the spacer suchthat the anterior portion and the spacer are a single piece. Theanterior portion has an upper surface, a lower surface, a first lateralportion, a second lateral portion, and at least one hole traversing theanterior portion for receiving a fastener. At least a portion of theupper surface or the lower surface of the anterior portion extendsbeyond the superior surface or the inferior surface of the spacer. Forexample, at least one beam may connect the anterior portion to theproximal end of the spacer to form a unitary piece.

The distal end of the spacer may have a first spring feature configuredto allow for compression and expansion of the spacer. For example, thefirst spring feature may be in the form of a v-spring. In addition, theproximal end of the spacer may include a second spring feature. Thesecond spring feature may also be in the form of a v-spring. Inparticular, the second spring feature may include more than one v-springoriented in opposite directions. The first and second spring featuresmay be configured such that the spacer simulates the modulus ofelasticity of bone even when the spacer and the anterior portion arecomprised of titanium.

According to another embodiment, an intervertebral implant forimplantation in an intervertebral space between adjacent vertebrae mayinclude a frame and at least one endplate. The frame may include a frontportion, a first arm extending from a first end of the front portion,and a second arm extending from a second end of the front portion. Thefront portion may at least partially define at least one fasteneraperture sized and dimensioned for receiving a fastener, such as a bonescrew or an anchor. The endplate includes at least one outer surfacehaving a contact area configured to engage adjacent vertebrae. Theendplate is affixed to the frame such that the endplate contacts atleast a portion of the plurality arms.

The frame may include a support member positioned centrally between thefirst and second arms. The support member may define at least oneopening to retain a corresponding protrusion on the which is configuredto provide for a friction fit between the endplate and the frame. Theopening may be elongated with a beveled perimeter such that acorresponding protrusion on the endplate is configured to be snappedinto the opening in the support member. The endplate may also defines atleast one indentation on a lateral portion of the endplate to retain acorresponding protrusion on the first and/or second arms which is alsoconfigured to provide an interference fit between the endplate and theframe. The first and second arms may join together at a rear portion toform a ring-like structure.

The endplates may include at least two endplates: a first endplateconfigured to fit in a first opening between the first arm and thesupport member and a second endplate configured to fit in a secondopening between the second arm and the support member. The endplate maybe inserted from the top, bottom, or back of the implant.

The front portion of the frame may be a unitary piece or may be dividedinto two separate portions with a passage positioned therebetween. Theendplate may include a central portion sized and configured to fitwithin the passage in the front portion. The central portion may definean opening sized and configured to receive an insert which accepts ananti-backout locking mechanism. In addition to the central portion, theendplate may include a first lateral wing and a second lateral wing. Thefirst lateral wing may be configured to contact a portion of the firstarm (e.g., forming at least a portion of an upper surface of theimplant) and the second lateral wing may be configured to contact aportion of the second arm (e.g., forming at least a portion of a lowersurface of the implant).

According to yet another embodiment, the implant may include a framehaving a superior surface, an inferior surface, a proximal end, and adistal end, wherein the superior surface and the inferior surface eachhave a contact area configured to engage adjacent vertebrae, and theframe defines at least one opening extending from the superior surfaceto the inferior surface of the frame. The frame includes a front surfacedefining at least one fastener aperture provided at an angle divergentto a horizontal plane for receiving a fastener. The endplates may besized and configured to fit within the openings in the frame, where theendplates are coupled to the frame by an interference fit and a ridgeprojecting around an outer perimeter of the endplate sized andconfigured to be received within a corresponding slot located within theopening. The slot may be located, for example, on a mid-transverse planeof the frame.

In any of the embodiments described herein, the implant may also includea locking mechanism, for example, disposed on the spacer, insert,member, or frame for preventing back out of the screws. For example, acam-style blocking mechanism may be used with screws that capture thefixation device screws once they are inserted fully into the implant.

The implants may be formed from any suitable biocompatible materials.For example, the implant may be manufactured from a biocompatible metal,such as titanium, polyether ether ketone (PEEK), bone or the like. Inone embodiment, the spacer or endplates is formed of a first materialand the insert, member, or frame is formed of a second materialdifferent from the first material. The insert, member, or frame may bemade of a stronger material designed to strength and reinforce one ormore openings in the spacer (e.g., designed to retain bone screws) or asattached to the endplates. For example, the spacer or endplates may beformed from PEEK and the insert, member, and frame may be formed fromtitanium. In the embodiment where the anterior portion and the spacerform a single piece, titanium may be selected for the entire implantbecause the one or more spring features provide for the spacer toemulate the elasticity of bone.

BRIEF DESCRIPTION OF DRAWING

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing. It is emphasizedthat, according to common practice, the various features of the drawingare not to scale. On the contrary, the dimensions of the variousfeatures are arbitrarily expanded or reduced for clarity. Included inthe drawing are the following figures:

FIG. 1A is a perspective view of a first embodiment suitable forcervical interbody fusion including a spacer with inserts configured toretain bone fasteners when secure to adjacent vertebrae;

FIG. 1B is a front view of the embodiment shown in FIG. 1A;

FIG. 1C is a top view of the embodiment shown in FIG. 1A;

FIG. 1D is an exploded view of the embodiment shown in FIG. 1A;

FIG. 1E is a lateral view of the embodiment shown in FIG. 1A;

FIG. 2A shows a perspective view of an alternative embodiment of aninterbody fusion device with inserts;

FIG. 2B is a top view of the embodiment shown in FIG. 2A;

FIG. 2C is an exploded view of the embodiment shown in FIG. 2A;

FIG. 2D is a front view of the embodiment shown in FIG. 2A;

FIG. 2E is a lateral view of the embodiment shown in FIG. 2A;

FIG. 3A is a perspective view of a third embodiment including a spacerwith recessed inserts;

FIG. 3B shows an exploded view of the embodiment shown in FIG. 3A;

FIG. 3C shows a front view of the embodiment shown in FIG. 3A;

FIG. 3D is a top view of the embodiment shown in FIG. 3A;

FIG. 3E is a lateral view of the embodiment shown in FIG. 3A;

FIG. 4A shows a perspective view of a fourth embodiment of an implantsuitable for lumbar interbody fusion including a spacer with threeinserts;

FIG. 4B is an exploded view of the embodiment shown in FIG. 4A;

FIG. 4C is a front view of the embodiment shown in FIG. 4A;

FIG. 4D is a bottom view of the embodiment shown in FIG. 4A;

FIG. 4E is a lateral view of the embodiment shown in FIG. 4A;

FIG. 5A is a perspective view of a fifth embodiment including insertswith head and arm portions;

FIG. 5B shows an exploded view of the embodiment shown in FIG. 5A;

FIG. 5C shows a top view of the embodiment shown in FIG. 5A;

FIG. 5D is a lateral view of the embodiment shown in FIG. 5A;

FIG. 5E is a front view of the embodiment shown in FIG. 5A;

FIG. 5F is a cross-sectional view as designated in FIG. 5E;

FIG. 6A is a perspective view of a sixth embodiment including a singleinsert recessed behind the front portion of the spacer;

FIG. 6B shows an exploded view of the embodiment shown in FIG. 6A;

FIG. 6C is a front view of the embodiment shown in FIG. 6A;

FIG. 6D is a lateral view of the embodiment shown in FIG. 6A;

FIG. 6E is a top view of the embodiment shown in FIG. 6A;

FIG. 7A shows a perspective view of a seventh embodiment withalternative inserts;

FIG. 7B shows an exploded view of the embodiment shown in FIG. 7A;

FIG. 7C is a front view of the embodiment shown in FIG. 7A;

FIG. 7D is a lateral view of the embodiment shown in FIG. 7A;

FIG. 7E is a top view of the embodiment shown in FIG. 7A;

FIG. 8A provides a perspective view of an eighth embodiment where theinserts are in the form of rings;

FIG. 8B shows an exploded view of the embodiment shown in FIG. 8A;

FIG. 8C is a front view of the embodiment shown in FIG. 8A;

FIG. 8D is a lateral view of the embodiment shown in FIG. 8A;

FIG. 8E is a top view of the embodiment shown in FIG. 8A;

FIG. 9A is a perspective view of a ninth embodiment where the insertshave a c-shaped configuration;

FIG. 9B shows an exploded view of the embodiment shown in FIG. 9A;

FIG. 9C is a front view of the embodiment shown in FIG. 9A;

FIG. 9D is a lateral view of the embodiment shown in FIG. 9A;

FIG. 9E is a top view of the embodiment shown in FIG. 9A;

FIG. 10A is a perspective view of a tenth embodiment including a singleinsert with a clamp-like design;

FIG. 10B is an exploded view of the embodiment shown in FIG. 10A;

FIG. 10C is a lateral view of the embodiment shown in FIG. 10A;

FIG. 11A shows an exploded view of an eleventh embodiment including atwo-part spacer and a member;

FIG. 11B shows a perspective view of the embodiment shown in FIG. 11A;

FIG. 11C is a front view of the embodiment shown in FIG. 11A;

FIG. 11D is a lateral view of the embodiment shown in FIG. 11A;

FIG. 11E is a top view of the embodiment shown in FIG. 11A;

FIG. 12A shows an exploded view of a twelfth embodiment where thetwo-part spacer is joined by a connecting member;

FIG. 12B shows a perspective view of the embodiment shown in FIG. 12A;

FIG. 12C is a front view of the embodiment shown in FIG. 12A;

FIG. 12D is a lateral view of the embodiment shown in FIG. 12A;

FIG. 12E is a top view of the embodiment shown in FIG. 12A;

FIG. 13A is a perspective view from an anterior position of a thirteenthembodiment of a single piece implant having an anterior portion and aspacer portion;

FIG. 13B is another perspective view from a posterior position of theembodiment shown in FIG. 13A;

FIG. 13C is a lateral view of the embodiment shown in FIG. 13A;

FIG. 13D is a top view of the embodiment shown in FIG. 13A;

FIG. 13E is another perspective view of the embodiment shown in FIG.13A;

FIG. 13F is a front view of the embodiment shown in FIG. 13A;

FIG. 13G is an alternative version of the embodiment shown in FIG. 13A;

FIG. 14 is an exploded view of a fourteenth embodiment of an implanthaving a frame with endplates configured to be affixed thereto;

FIGS. 15A and 15B are exploded views of a fifteenth embodiment showingimplants having a frame defining a ring-like shape where the endplatesare secured with an interference fit;

FIGS. 16A and 16B show exploded views of a sixteenth embodimentincluding implants having a frame including arms and a support memberwhere the endplates are secured with an interference fit;

FIGS. 17A and 17B show exploded views of a seventeenth embodimentincluding implants having a frame including arms and a centrally locatedsupport member and two endplates securable with interference features onthe support member and the arms; and

FIGS. 18A and 18B show exploded views of an eighteenth embodiment havinga frame with a plurality of endplates configured to be received withinthe openings in the frame.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the disclosure are generally directed to stand-aloneinterbody fusion implants. Specifically, the implants include a spacercombined with at least one insert or member. The inserts or members maybe included, for example, to provide openings such as through holeswhich are designed to retain bone fasteners, such as screws, anchors,staples, pins, nails, and the like. According to other embodiments, theimplants include a frame combined with one or more endplates. The frameincludes a portion with openings such as through holes which aredesigned to retain bone fasteners, such as screws, anchors, staples,pins, nails, and the like. The frame may also include arms and anoptional support member designed to secure the endplates, for example,with an interference fit.

The embodiments of the disclosure and the various features andadvantageous details thereof are explained more fully with reference tothe non-limiting embodiments and examples that are described and/orillustrated in the accompanying drawings and detailed in the followingdescription. The features of one embodiment may be employed with otherembodiments as the skilled artisan would recognize, even if notexplicitly stated herein. Descriptions of well-known components andprocessing techniques may be omitted so as to not unnecessarily obscurethe embodiments of the disclosure. The examples used herein are intendedmerely to facilitate an understanding of ways in which the disclosuremay be practiced and to further enable those of skill in the art topractice the embodiments of the disclosure. Accordingly, the examplesand embodiments herein should not be construed as limiting the scope ofthe disclosure, which is defined solely by the appended claims andapplicable law. Moreover, it is noted that like reference numeralsrepresent similar parts throughout the several views of the drawings.

As used herein and in the claims, the terms “comprising” and “including”are inclusive or open-ended and do not exclude additional unrecitedelements, compositional components, or method steps. Accordingly, theterms “comprising” and “including” encompass the more restrictive terms“consisting essentially of” and “consisting of.”

Certain embodiments may be used on the cervical, thoracic, lumbar,and/or sacral segments of the spine. For example, the size and massincrease of the vertebrae in the spine from the cervical to the lumbarportions is directly related to an increased capacity for supportinglarger loads. This increase in load bearing capacity, however, isparalleled by a decrease in flexibility and an increase insusceptibility to strain. When rigid immobilization systems are used inthe lumbar segment, the flexibility is decreased even further beyond thenatural motion restriction of that segment. Replacing the conventionalrigid immobilization systems with certain embodiments disclosed hereinmay generally restore a more natural movement and provide added supportto the strain-susceptible areas.

Nom FIGS. 1A-1E illustrate different views of one particular embodimentof the stand-alone intervertebral implant 1. As shown in the perspectiveview of FIG. 1A, the implant 1 includes a spacer 12 and one or moreinserts 50. The inserts 50 may be especially designed and configured todefine a fastener aperture 34 and/or stabilize, strengthen, and/orreinforce the spacer 12.

The spacer 12 includes a superior surface 42 and an inferior surface 44.The superior and inferior surfaces 42, 44 each have a contact area 22configured to contact and engage adjacent vertebrae (not shown). Thesuperior and inferior surfaces 42, 44 may be parallel, curved, or angledto help restore or recreate a lordosis angle (or other angle) of thehuman spine. In particular, the superior and inferior surfaces 42, 44may have a convex curve on the upper and lower surfaces or may be angledfrom a distal end to a proximal end or from one lateral side to theother to account for curvature of the spine. In addition, the superiorand/or inferior surfaces 42, 44 may be contoured to conform more closelyto the concave endplates of the adjacent vertebra.

In order to engage the adjacent vertebrae, the spacer 12 may include aplurality of protrusions 13 or teeth on the contact areas 22 of thesuperior and/or inferior surfaces 42, 44. The protrusions 13 on thesuperior and inferior surfaces 42, 44 of each implant 1 grip theendplates of the adjacent vertebrae, resist migration, and aid inexpulsion resistance. The plurality of protrusions 13 may be pyramidalin shape, but the protrusions 13 can be configured to be any size orshape to enhance anchoring the spacer 12 and the implant 1 to each ofthe adjacent vertebrae.

The implant 1 may contain an opening 16. The opening 16 may be in theform of an axial graft hole within the spacer 12 configured to providethe maximum amount of volume for bone graft packing. The opening 16 maybe configured for receiving bone graft material, for example, to promotefusion of the adjacent vertebral bodies. The opening 16 may extend fromthe superior surface 42 to the inferior surface 44 of the spacer 12 todefine a substantially hollow center suitable for retaining one or morebone graft materials. For example, cadaveric bone, autologous bone, boneslurry, BMP, or other similar materials, may enhance tissue growthwithin the intervertebral space.

The spacer 12 includes a distal end 46 and a proximal end 48. The distalend 46 of the spacer 12 may include a leading taper 40 for ease ofinsertion into the disc space. The leading taper 40 may be in the formof a chamfer or a bevel which enables self-distraction of the adjacentvertebral bodies during insertion of the implant 1. The leading taper 40may be located along the insertion direction of the implant 1. Forexample, the leading taper 40 may assist in an anterior approach to thedisc space.

As provided in FIG. 1D, the spacer 12 defines at least one cutout 24extending from the proximal end 48 to the opening 16. In particular, thecutout 24 may be in fluid communication with the opening 16. The cutouts24 may also be defined through a portion of the lateral sides 36, 38 tothe opening 16. The cutouts 24 may be of any suitable shape andconfiguration, but are preferably sized and dimensioned to receive andretain at least a portion of the insert 50. For example, the cutout 24may be sized and dimensioned to receive one or more faces or sides ofthe insert 50. The cutout 24 may be uniform or non-uniform and maycomprise any morphology of recesses and protrusions configured to matewith the insert 50, for example, including a male/female mating. Forexample, the cutout 24 may be defined by one or more stepped projections26 on the spacer 12. The cutout 24 may be defined such that the spacer12 remains a single continuous piece (FIG. 1D) or the cutout 24 may bedefined such that the spacer is broken into separate sections or pieces(not shown).

The insert 50 may be configured to comprise a fastener aperture 34,which is sized and dimensioned for receiving a fastener, such as a screw30. Thus, the implant 1 may be secured to the adjacent vertebrae usingfasteners, such as screws, anchors, staples, pins, nails, or the like.

The insert 50 is provided with a given depth and dimension designed tointegrate seamlessly with the spacer 12. In particular, the depth of theinsert 50 may be greater than the width and/or height of the insert 50.In addition, the insert 50 may not span across an entire frontage of thespacer 12. Instead, the inserts 50 may be provided as discrete unitsdesigned to marry with the spacer 12 only at locations needed toreinforce and/or position bone fasteners, such as screws 30. Thus, theinserts 50 may form only a portion of the front or an area proximate tothe front of the implant 1. In the embodiment shown in FIG. 1A when twoinserts 50 are present, the inserts 50 may be separated a distance apartwith a portion of spacer 12 positioned between the two inserts 50.

A shown in FIG. 1D, the insert 50 may include a head portion 52 and atleast one arm 54 projecting therefrom. The head portion 52 may beenlarged to define the opening or fastener aperture 34 configured forretaining the fastener. The head portion 52 may include a cylindricalportion forming the fastener aperture 34. The arm 54 may extend from thehead portion 52 in one or more directions to contact and integrate withthe spacer 12. For example, the arm 54 may extend laterally, medially,and/or posteriorly away from the head portion 52. In particular, the arm54 may extend posteriorly away from the head portion 52 and toward thedistal end 46 of the spacer 12 when attached thereto.

The insert 50 including a portion of the arm 54 and/or a portion of thehead portion 52 may be configured to mirror the shape and design of thespacer 12. The spacer 12 may define at least one recess, projection,etc. sized and dimensioned to retain at least a portion of the arm 54.For example, the arm 54 or any portion of the insert 50 may rest againsta portion of the spacer 12 or a recess formed therein to provide ajoint, such as a lap joint, half lap joint, dovetail lap joint, beveledlap joint or scarf joint, stepped lap joint, tabled lap joint, or thelike. In particular, a lap joint may include joining two pieces ofmaterial together by at least partially overlapping them (e.g., at leasta portion of the insert 50 and a portion of the spacer 12 areoverlapped). In a full lap, no material is removed from either of themembers to be joined, resulting in a joint which is the combinedthickness of the two members. In a half lap joint, material is removedfrom each of the members so that the resulting joint is the thickness ofthe thickest member. In the embodiment shown in FIG. 1E, the jointportion between the insert 50 and the spacer 12 is at least partially ahalf lap joint such that the joint does not increase the height of thespacer 12.

As shown in FIG. 1E, the insert 50 may join the spacer 12 with a steppedlap joint. A portion of the insert 50 may be stepped with a maleprojection to mate with a stepped female configuration of the spacer 12.A series of offset planar surfaces having a rise and a run may form thestepped profile. For example, the arm 54 of the insert 50 may be steppedwith a male projection configured to mate with corresponding steppedprojections 26 on the spacer 12. Depending on the configuration of thejoint, the joint may form a press-fit or friction-fit engagement tosecure the insert 50 to the spacer 12 or the joint may be furthersecured, for example, with adhesive, pins 78, or the like.

The insert 50 is coupled to the spacer 12 such that at least a portionof the insert 50 is received in the cutout 24 in the spacer 12. Thespacer 12 and the insert 50 may be coupled, removably coupled,connected, or attached together in any suitable manner known in the art.The spacer 12 and the insert 50 may also be coupled together throughappropriate coupling means or fasteners. For example, the insert 50 andcutout 24 may be configured to provide male and female edges, which arethe mechanical interfaces between the two pieces. Portions of the spacer12 and the insert 50 may be assembled together using, alone or incombination, a friction fit, a dovetail assembly, dowel pins, hooks,staples, screws, adhesives, and the like, or any suitable fastenersknown in the art, which can be used to permanently attach the spacer 12and the insert 50 together.

In addition or in the alternative, the spacer 12 and the inserts 50 maybe secured together with pins 78 which traverse at least a portion ofthe spacer 12 and/or the insert 50. For example, the arm 54 may includeone or more openings 80 extending therethrough sized and configured toreceive a portion of pin 78. Similarly, the corresponding portion of thespacer 12 may include one or more openings 80 extending therethroughsized and configured to receive the remainder of pin 78 to secure thearm 54 to the spacer 12. These openings 80 may or may not be threaded.The pins 78 may pass through holes 80, for example, in a substantiallyperpendicular manner relative to a horizontal plane to secure the jointbetween the insert 50 and the spacer 12. For example, the pins 78 may beoriented substantially perpendicular relative to the superior and/orinferior surfaces 42, 44 of the spacer 12. The pins 78 may be in theform of dowels or may be fully or partially threaded. The pins 78 may beformed from a biocompatible material, such as titanium, or the pins 78may be formed from tantalum, for example, to enable radiographicvisualization.

The head portion 52 of the insert 50 may include an upper surface 62 anda lower surface 64 depending on the orientation of the insert 50. Forexample, the two inserts 50 depicted in FIG. 1D are identical except theinserts 50 are oriented in opposite directions to fit the respectivecutouts 24 in the spacer 12. The first insert 50 a is oriented such thatthe upper surface 62 is configured to mate with a portion of thesuperior surface 42 of the spacer 12 and the lower surface 64 isconfigured to mate with a portion of the inferior surface 44 of thespacer. Conversely, the second insert 50 b is oriented such that thelower surface 64 is configured to mate with a portion of the superiorsurface 42 of the spacer 12 and the upper surface 62 is configured tomate with a portion of the inferior surface 44 of the spacer.

The upper surface 62 and/or lower surface 64 of the head portion 52 ofthe insert 50 may extend a distance beyond the superior surface 42, theinferior surface 44, or both surfaces 42, 44 of the spacer 12. Inparticular, a portion of the head portion 52 of the insert 50 may extendabove or below the superior and inferior surfaces 42, 44 of the spacer12. For example, the lower surface 64 of the first insert 50 a mayextend beyond the inferior surface 44 and the lower surface 64 of thesecond insert 50 b may extend beyond the superior surface 42 of thespacer 12.

The projection of the lower surfaces 64 of the first and second inserts50 a, 50 b may be in the form of an eyebrow 60. The eyebrows 60 mayfully capture the bone screws 30 while still allowing for the screw 30to reside about, below, or above the base plane of the superior andinferior surfaces 42, 44. For example, a front surface 65 of the insert12 may include at least one eyebrow 60 where the eyebrow 60 projectspast the superior surface 42, the inferior surface 44, or both surfaces42, 44 of the spacer 12. The eyebrow 60 may include a rounded portion.The eyebrow 60 may include a smooth surface or a roughened surface. Asshown in FIG. 1B, the eyebrow 60 may be comprised of a smooth and curvedsurface. A lateral portion of the eyebrow 60 may further include one ormore torsional stabilizers 70 configured to prevent or minimizetorsional motion of the implant 1 once implanted. The torsionalstabilizers 70 may act as extensions or fins, which may serve as knifeedges to further purchase into the bone of the adjacent vertebrae orserve as a stop to abut anterior aspects of the adjacent vertebrae. Thetorsional stabilizer 70 may include a spiked or pointed projection orextension configured to engage adjacent vertebrae. In particular, thetorsional stabilizer 70 may have a width substantially the same or lessthan a width of the eyebrow 60.

A portion of each of the upper surfaces 62 of the inserts 50 may alsoinclude an additional torsional stabilizer 70, for example, positionedopposite to the eyebrows 60. The torsional stabilizer 70 on the uppersurfaces 62 may be the same or different than the torsional stabilizer70 extending from the eyebrows 60. The upper surfaces 62 of the inserts50 may complete a surface of the superior and inferior surfaces 42, 44of the spacer 12 to enhance anchoring of the spacer 12. As shown in FIG.1D, the spacer 12 may include a notch 23 in the cutout 24 in thesuperior and/or inferior surfaces 42, 44 of the spacer 12. The extensionof the upper surface 62 including the torsional stabilizer 70 may fit inthis notch 23 to form a continuous and contiguous superior and/orinferior surface for the implant 1. The notch 23 may be uniform in shapeand dimension or non-uniform. In particular, the notch 23 may have apartial rectangular cross-section or may be any suitable shape tocompliment the upper surface 62 of the insert 50 and complete thesuperior and/or inferior surfaces 42, 44 of the spacer 12.

Each insert 50 includes a screw hole or fastener aperture 34 sized anddimensioned to receive a fastener, such as screw 30. The screws 30 maybe any suitable screws known in the art including fixed or variableangle. The screw hole 34 is configured to receive the screw 30 at agiven angle. For example, the screw holes 34 for receiving the screw 30may traverse the front surface 65 of the insert 50 at an angle divergentto a horizontal plane in order to secure the implant 1 to one of theadjacent vertebrae. Thus, in the case of implant 1 having two inserts 50as shown in FIG. 1A, the screws 30 enter the screw holes 34 at specifiedangles to enter each of the adjacent vertebrae at the optimal locations.In particular, the screws 30 may be inserted at an angle for maximumscrew purchase into the superior and inferior vertebral bodies.

The intervertebral implant 1 may be positioned in the spine after thedisc portion between the two vertebral bodies is exposed and removed,for example, using rongeurs or other suitable instruments. The posteriorand lateral walls of the annulus are generally preserved to provideperipheral support for the implant 1 and graft materials. A trial deviceattached to a trial holder may then be inserted into the disc space todetermine size of the implant 1. This procedure is generally conductedusing fluoroscopy and tactile feel. The implant 1 may be available invarious heights and geometric options to fit the anatomical needs of awide variety of patients. After the appropriate sized implant 1 isselected and attached to an implant holder and drill guide (not shown),the implant 1 may be inserted into the disc space. Before or after theimplant 1 is positioned within the disc space, supplemental graftmaterial can be used to enhance fusion. The implant 1 may be implantedin the vertebral space using an anterior, posterior, lateral,anterolateral, oblique, and/or transforaminal approach. The implant 1shown in FIG. 1A may be particularly suitable for an anterior cervicalprocedure. The implant 1 may be in the form of a stand-alone fusiondevice to provide structural stability and a low or zero profile design.The implant 1 is preferably assembled before insertion into the discspace.

Once the implant 1 is positioned inside the disc space, an awl or anysimilar type of instrument, for example, can be used to drill throughthe screw hole and break the cortex of the adjacent vertebral body. Thesurgeon performing this procedure may then use a depth gauge todetermine the screw length. Once the appropriate screw length isdetermined, screws 30 may be inserted using a self-retainingscrewdriver, for example. Any suitable type of screw 30 may be selectedby one of ordinary skill in the art. For example, the screws 30 mayinclude fixed or variable angle screws of any suitable size withappropriate thread spacing, thread pitch, head design, length, and thelike.

Once inserted, the screws 30 may be secured with an anti-back outprevention or locking mechanism 20. The locking mechanism 20 may be inthe form of one or more blocking screw 32 to capture the sides of theinserted screws to prevent screw back out. As depicted in FIG. 1B, thelocking mechanism 20 may be disposed on the spacer 12 for preventingback out of the screws 30. For example, a cam-style blocking mechanismmay be used with screws 30 that capture the fixation device screws 30once they are inserted fully into the inserts 50. The insert 50 mayinclude a cutout 56 in the outer periphery of the head portion 52configured such that the locking mechanism 20 may block or unblock thehead of the screw 30. As shown, the anti-back out mechanism 20 mayinclude a single set screw 32 that retains the screws 30 with theimplant 1, although any suitable anti-back out mechanism 20 may beselected by one of ordinary skill in the art.

FIGS. 2A-2E show alternative views of a second embodiment of an implant10. In general, most of the structure of implant 10 is similar orcomparable to the structure of implant 1. In this particular embodiment,the torsional stabilizers 70 on the upper surfaces 62 are replaced witha plurality of protrusions 13 or teeth. As shown in FIG. 2B, a portionof the upper surfaces 62 of the inserts 50 a, 50 b may include anextension with a plurality of protrusions 13 or teeth designed to extendthe contact areas 22 of the superior and/or inferior surfaces 42, 44 ofthe spacer 12. The protrusions 13 on the upper surfaces 62 of theinserts 50 a, 50 b may complete a surface of the superior and inferiorsurfaces 42, 44 of the spacer 12 to enhance anchoring of the spacer 12.As shown in FIG. 2C, the spacer 12 may include the notch 23 in thecutout 24 in the superior and/or inferior surfaces 42, 44 of the spacer12. The notch 23 may be uniform in shape and dimension or non-uniform.In particular, the notch 23 may have a partial rectangularcross-section. The extension of the upper surface 62 including theplurality of protrusions 13 may fit in this notch 23 to form acontinuous and contiguous superior and/or inferior surface for theimplant 10. The plurality of protrusions 13 may be the same or differentthan the protrusions 13 provided on the remainder of the spacer 12.

According to a third embodiment, FIGS. 3A-3E show alternative views animplant 100. In general, most of the structure of implant 100 is similaror comparable to the structure of implant 1. In this particularembodiment, different inserts 150 are provided. In particular, the uppersurfaces 162 of the inserts 150 a, 150 b do not include a plurality ofprotrusions and are instead smooth. These smooth upper surfaces 162 donot complete the superior and inferior surfaces 142, 144 of the spacer112. Instead, the smooth upper surfaces 162 are recessed and matedbeneath the superior and inferior surfaces 142, 144 of the spacer 112.In addition, the cutouts 124 are modified from those shown in implant 1.For example, the superior and inferior surfaces 142, 144 of the spacer112 are not notched to receive a portion of the insert 150, but insteadextend to the proximal end 48 of the spacer. As is evident in FIG. 3B, aportion of the stepped projection 126 on the spacer 112 is extended tobe contiguous and flush with the proximal end 48 of the spacer 112.

According to a fourth embodiment, FIGS. 4A-4E show an implant 200, whichmay be particularly suitable for an anterior lumbar procedure. Ingeneral, most of the structure of implant 200 is similar or comparableto the structure of implant 1. In this particular embodiment, threedifferent inserts 250 provide the fastener apertures 234.

A shown in FIG. 4B, a first insert 250 a is identical to a second insert250 b except as mirror images of one another to fit the respectivecutouts 224 in the spacer 212. The first and second inserts 250 a, 250 beach define a fastener aperture 234. The first and second inserts 250 a,250 b are each configured to allow a bone screw 230 to engage superioror inferior vertebra. Similar to implant 1, the spacer 212 may includeone or more cutouts 224 sized and configured to retain the inserts 250.The cutouts 224 may further define a stepped projection 226 configuredto mate with the arm 254 of the insert 250. The arm 254 may also bestepped and configured to mate with corresponding stepped projections226 on the spacer 212. A portion of the insert 250 may be stepped with amale projection to mate with a stepped female configuration of thespacer 212. The arm 254 may include a series of offset planar surfaces,for example, having a rise and a run, to form the stepped profile. Thecutouts 224 may be in fluid communication with the opening 216 extendingfrom the superior surface 242 to the inferior surface 244 of the spacer212.

In addition, the spacer 212 may include one or more notches 223 in thecutout 224 in the superior surface 242 and/or inferior surface 244 ofthe spacer 212. The extension of the upper surface 262 of the insert 250including the plurality of protrusions 213 may fit in the respectivenotch 223 to form a continuous and contiguous superior surface for theimplant 200. A third insert 250 c is provided between the first andsecond inserts 250 a, 250 b. The third insert 250 c is different fromthe first and second inserts 250 a, 250 b and allows a bone screw 230 toengage a superior vertebra. Although the third insert 250 c is depictedwith a smooth upper surface 262, the third insert 250 c may also includeprojections 213, torsional stabilizers, or the like.

The fastener apertures 234 may be configured such that the lockingmechanism 220 may block or unblock the heads of the screws 230 in therespective fastener apertures 234. As shown, the anti-back out mechanism220 may include a first set screw 232 a that is configured to block aportion of the screw 230 in the first insert 250 a and the screw 230 inthe third insert 250 c and a second set screw 232 b that is configuredto block a portion of the screw 230 in the second insert 250 b and thescrew 230 in the third insert 250 c.

FIGS. 5A-5F show a fifth embodiment of an implant 300. In general, mostof the structure of implant 300 is similar or comparable to thestructure of implant 1. In this particular embodiment, two differentinserts 350 provide the fastener apertures 334. In this case, modifiedarms 354 are at least partially received in at least one recess 318 inthe spacer 312 to join the insert 350 to the spacer 312. The recess 318may extend a set depth into the spacer 312 from the opening 316. Therecess 318 may be in fluid communication with the opening 316. Therecess 318 may be formed in the lateral portions and/or the distalportion of the opening 316. The recess 318 may be positionedsubstantially medially between and substantially parallel to thesuperior and/or inferior surfaces 342, 344 of the spacer 312. The recess318 may be sized and dimensioned to retain at least a portion of the arm354 of the insert 350.

The two inserts 350 depicted in FIG. 5B are identical except areoriented in opposite directions to fit the respective cutouts 324 in thespacer 312. The insert 350 may include head portion 352 and arm 354extending therefrom. The arm 354 may extend posteriorly away from thehead portion 352 and toward the distal end 346 of the spacer 312 whenattached thereto. The arm 354 may be angled relative to the head portion352 such that the arm 354 is oriented in a medial direction, forexample, to mimic the shape of the spacer 312.

Each arm 354 of the insert 350 may include a first arm portion 354 a anda second arm portion 354 b. The first arm portion 354 a may connect thehead portion 352 of the insert 350 to the second arm portion 354 b. Thesecond arm portion 354 may be angled relative to the first arm portion354 a. The first arm portion 354 a may engage the lateral portions ofthe recess 318 in the spacer 312, and the second arm portion 354 b mayengage the distal portion of the recess 318 in the spacer 312. The uppersurface 362 of the insert 350 including the head portion 352, the firstarm portion 354 a, and the second arm portion 354 b may be a continuousand contiguous coplanar surface. In the alternative, the arm 354 may berecessed beneath the upper surface 362 of the head portion 352. The arms354 of the inserts 350 may join the spacer 312 via a press-fit orfriction-fit engagement to secure the insert 350 to the spacer 312 orthe joint may be further secured, for example, with adhesive, pins, orthe like.

Similar to implant 1, the lower surface 364 of the head portion 352 ofthe insert 350 may extend a distance beyond the superior surface 342,the inferior surface 344, or both surfaces 342, 344 of the spacer 312.For example, the lower surface 364 of the first insert 350 a may extendbeyond the inferior surface 344 and the lower surface 364 of the secondinsert 350 b may extend beyond the superior surface 342 of the spacer312. The projection of the lower surfaces 364 of the first and secondinserts 350 a, 350 b may be in the form of eyebrows 360. In thisembodiment, the eyebrow 360 includes a substantially smooth and curvedsurface. In the embodiment shown, no torsional stabilizers are present,but one or more torsional stabilizers may be added if desired.

Similar to implant 100, the upper surfaces 362 of the inserts 350 a, 350b do not include a plurality of protrusions and are instead smooth.These smooth upper surfaces 362 do not complete the superior andinferior surfaces 342, 344 of the spacer 312. Instead, the smooth uppersurfaces 362 are recessed and mated beneath the superior and inferiorsurfaces 342, 344 of the spacer 312. In addition, the cutouts 324 aredifferent from those shown in implant 1. For example, the superior andinferior surfaces 342, 344 of the spacer 312 are not notched to receivea portion of the insert 350, but extend to the proximal end 348 of thespacer.

FIGS. 6A-6E show a sixth embodiment of an implant 400 including a singlemember 450 recessed behind the front portion of the spacer 412. Ingeneral, most of the structure of implant 400 is similar or comparableto the structure of implant 1. Unlike the individual inserts 50 providedfor each fastener aperture 34 in implant 1, in this particularembodiment, a single member 450 provides all of the fastener apertures434.

In this embodiment, the single member 450 provides two fastenerapertures 434 to secure fasteners in both the superior and inferiorvertebrae. This member 450 may be provided with or without arms. Themember 450 may be recessed in the spacer 412 and positioned posterior tothe front surface 465 of the spacer 412. In particular, the member 450may be positioned within the opening 416 such that a first portion ofthe member 450 is received in a first cutout 424 in the spacer 412 and asecond portion of the member 450 is received a second cutout 424 in thespacer 412. The member 450 may be curved and contoured to follow aproximal portion of the spacer 412.

Similar to implant 1, the upper and/or lower surfaces 462, 464 of themember 450 may extend a distance beyond the superior surface 442, theinferior surface 444, or both surfaces 442, 444 of the spacer 412. Forexample, a portion of the upper surface 462 of the member 450 may extendabove the superior surface 442 and a portion of the lower surface 464may extend below the inferior surface 444 of the spacer 412. Theprojections of the upper and lower surfaces 462, 464 of the singlemember 450 may be in the form of eyebrows 460. In this embodiment, theeyebrows 460 include a substantially smooth and curved surface. In theembodiment shown, torsional stabilizers 470 are provided opposite to theeyebrows 460 and are also provided substantially medially on the member450 projecting superiorly and inferiorly from both the upper and lowersurfaces 462, 464, respectively. The torsional stabilizers 470 mayinclude a spiked or pointed projection or extension configured to engageadjacent vertebrae.

According to a seventh embodiment, FIGS. 7A-7E depict an implant 500with a different type of insert 550. In general, most of the structureof implant 500 is similar or comparable to the structure of implant 1.Unlike the inserts 50 provided with arm 54 in implant 1, in thisparticular embodiment, the insert 550, which provides the fasteneraperture 534, does not contain an arm and is directly recessed into atleast one slot 518 in the spacer 512.

The two inserts 550 depicted in FIG. 7B are identical except areoriented in opposite directions to fit the respective cutouts 524 in thespacer 512. The insert 550 may be curved or may contain one or moreangled transitions. At least a portion of the inserts 550 may join thespacer 512 via a press-fit or friction-fit engagement to secure theinsert 550 to the spacer 512 or the joint may be further secured, forexample, with adhesive, pins, or the like.

In this embodiment, the inserts 550 are at least partially received inat least one slot 518 in the spacer 512 to join the insert 550 to thespacer 512. The slot 518 may extend a set depth into the spacer 512 fromthe cutout 524. For example, the slot 518 may be formed in an inferioror superior portion of the cutout 524 and may be in fluid communicationwith the cutout 524. The slot 518 may include more than one portionincluding an angled portion, for example. The angled portion may connectthe eyebrow 560 to a planar portion. The planar portion may bepositioned substantially perpendicular to the superior and/or inferiorsurfaces 542, 544 of the spacer 12. The slot 518 may be sized anddimensioned in any suitable configuration to retain at least a portionof the insert 550. For example, the upper surface 562 of the insert 550may contact and fit within the slot 518. The upper surfaces 562 of theinserts 550 may be substantially smooth or may be textured. The uppersurface 562 may also be curved or rounded as shown. These smooth uppersurfaces 562 are recessed and mated beneath the superior and inferiorsurfaces 542, 544 of the spacer 512.

In this embodiment, the depth of the insert 550 may be the same orsmaller than the depth of the proximal portion of the spacer. In otherwords, the insert 550 does not need to fill the entire depth of thecutout 524. As shown in FIG. 7E, the insert 550 fills only a portion ofthe cutout 524. In this embodiment, the insert 550 is positionedsubstantially centrally in the cutout 524, but it is envisioned that theinsert 550 may be positioned at any suitable location in the cutout 524.

Similar to implant 1, the lower surface 564 of the insert 550 may extenda distance beyond the superior surface 542, the inferior surface 544, orboth surfaces 542, 544 of the spacer 512. For example, the lower surface564 of the first insert 550 a may extend below the inferior surface 544and the lower surface 564 of the second insert 550 b may extend abovethe superior surface 542 of the spacer 512. The projection of the lowersurfaces 564 of the first and second inserts 550 a, 550 b may be in theform of an eyebrow 560. In this embodiment, the eyebrow 560 includes asubstantially smooth and curved surface. In the embodiment shown, notorsional stabilizers are present, but one or more torsional stabilizersmay be added if desired.

FIGS. 8A-8E provide an eighth embodiment of an implant 600 where theinserts 650 are in the form of rings. In general, most of the structureof implant 600 is similar or comparable to the structure of implant 1.In addition, this embodiment is similar to the implant 500 discussedabove.

In this embodiment, the insert 650 is in the form of a ring or cylinder.The ring insert 650 may be provided with one or more slits 658, forexample, to allow the insert 650 to tightly mate with the cutout 624through the spacer 612 and secure the insert 650 to the spacer 612. Inparticular, one or more slits 658 may be longitudinally positionedaround a periphery of the ring-shaped insert 650. The slits 658 may beuniformly or non-uniformly positioned around the insert 650. As shown inFIG. 8B, the slits 658 may be positioned in 90° increments around thering insert 650. For example, four slits 658 may be positioned aroundthe periphery of the ring insert 650. The slits 658 may be oriented suchthat the open ends of the slits 658 face anteriorly.

The insert 650 may be received in a recess in the cutout 624 or may bepositioned within the cutout 624. The cutouts 624 may be in fluidcommunication with the opening 616 extending from the superior surface642 to the inferior surface 644 of the spacer 612. The insert 650 may beconfigured to at least partially define and reinforce the fasteneraperture 634. At least a portion of the inserts 650 may join the spacer612 via a press-fit or friction-fit engagement to secure the insert 650to the spacer 612. The insert 650 may be further secured, for example,with adhesive or the like.

In this embodiment, the depth of the insert 650 may be the same orsmaller than the depth of the proximal portion of the spacer. In otherwords, the insert 650 does not need to fill the entire depth of thecutout 624. In this embodiment, the insert 650 is positioned at an anglein the cutout 624 to accommodate the angles of the bone screws 630. Itis envisioned that the insert 650 may be positioned at any suitablelocation in the cutout 624.

FIGS. 9A-9E provide a ninth embodiment of an implant 700. In general,most of the structure of implant 700 is similar or comparable to thestructure of implant 1. In addition, this embodiment is substantiallythe same as the implant 600 discussed above, and the discussion forimplant 600 applies equally here. In this particular embodiment, theinsert 750 has a c-shaped cross-section instead of being in the form ofa ring. The c-shaped inserts 750 shown in FIG. 9B are the same exceptare oriented differently. The c-shaped inserts 750 are substantially thesame as the ring inserts 650 except a gap separates the insert 750 toallow for further compression and/or expansion of the insert 750.

The c-shaped insert 750 may also be provided with one or more slits 758,for example, to allow the insert 750 to tightly mate with the cutout 724through the spacer 712 and secure the insert 750 to the spacer 712. Inparticular, one or more slits 758 may be longitudinally positionedaround a periphery of the c-shaped insert 750. The slits 758 may beuniformly or non-uniformly positioned around the insert 750. The slits758 may also positioned in 90° increments around the c-shaped insert750. For example, three slits 758 may be positioned around the peripheryof the ring insert 750. The slits 758 may be oriented such that the openends of the slits 758 face anteriorly.

The insert 750 may be received in a recess in the cutout 724 or may bepositioned within the cutout 724. The cutouts 724 may be in fluidcommunication with the opening 716 extending from the superior surface742 to the inferior surface 744 of the spacer 712. The insert 750 may beconfigured to at least partially define the fastener aperture 734. Atleast a portion of the inserts 750 may join the spacer 712 via apress-fit or friction-fit engagement to secure the insert 750 to thespacer 712. The insert 750 may also be secured, for example, withadhesive or the like. In this embodiment, the depth of the insert 750may be the same or smaller than the depth of the proximal portion of thespacer. Similar to insert 650, the c-shaped insert 750 does not need tofill the entire depth of the cutout 724. In this embodiment, the insert750 is positioned at an angle in the cutout 724 to accommodate theangles of the bone screws 730, but it is envisioned that the insert 750may be positioned at any suitable location in the cutout 724 so long asthe necessary reinforcement is provided to the fasteners.

According to a tenth embodiment, FIGS. 10A-10C provide an implant 800with a member 850. In general, most of the structure of implant 800 issimilar or comparable to the structure of implant 1. Unlike theindividual inserts 50 provided for each fastener aperture 34 in implant1, in this particular embodiment, a member 850 provides all of thefastener apertures 834. The member 850 may be in the form of a clamp orclip, which surrounds a proximal portion of the spacer 812.

In this embodiment, the member 850 provides two fastener apertures 834to secure fasteners in both the superior and inferior vertebrae. Thismember 850 may be provided with or without arms. The member 850 may bepositioned posterior to the front surface 865 of the spacer 812. Inparticular, the member 850 may be positioned to surround or envelop aportion of at least one lateral side 836, 838 and a portion of thesuperior and/or inferior surfaces 842, 844 of the spacer 812. The member850 may be contoured, for example, to begin at one lateral side 836 wraparound a portion of the superior surface 842 to define one of thefastener apertures 834, wrap around the other lateral side 838, wrapunder a portion of the inferior surface 844 to define the other fasteneraperture 834, and terminate at the lateral side 836. The member 850 maybegin and terminate at one lateral side 836, 838, for example, using oneor more clamping features 882. The clamping features 882 may includeprongs or springs which attach or secure the member 850 to the spacer812. Although the member 850 is depicted as a single piece, it isenvisioned that the clamping member 850 may be comprised of more thanone part so long as the member 850 may clamp to the spacer 812 andprovide the fastener apertures 834.

A portion of the upper and/or lower surfaces 862, 864 of the member 850may extend a distance beyond the superior surface 842, the inferiorsurface 844, or both surfaces 842, 844 of the spacer 812. For example, aportion of the upper surface 862 may extend above the superior surface842 and a portion of the lower surface 864 may extend below the inferiorsurface 844 of the spacer 812. The projections of the upper and lowersurfaces 862, 864 of the single insert 850 may be in the form ofeyebrows 860. In this embodiment, the eyebrows 860 include asubstantially smooth and curved surface. In the embodiment shown,torsional stabilizers 870 are also provided substantially medially andlaterally on the member 850 projecting superiorly and inferiorly fromboth the upper and lower surfaces 862, 864, respectively. The torsionalstabilizers 870 may include a spiked or pointed projection or extensionconfigured to engage adjacent vertebrae.

FIGS. 11A-11E provide an eleventh embodiment of an implant 900. Ingeneral, the structure of implant 900 is similar or comparable to thestructure of implant 1. In this embodiment, the inserts 50 have beenreplaced with a member 950 and the spacer 912 includes multiplecomponents.

The spacer 912 has a first spacer portion 972 and a second spacerportion 974. The first spacer portion 972 has a first end 972 a and asecond end 972 b, and the second spacer portion 974 has a first end 974a and a second end 974 b. The second end 972 b of the first spacerportion 972 is coupled to the first end 974 a of the second spacerportion 974. The first and second spacer portions 972, 974 form thesuperior surface 942 and the inferior surface 944 of the spacer 912. Thesuperior surface 942 and the inferior surface 944 each have a contactarea 922 configured to engage adjacent vertebrae. The first and secondspacer portions 972, 974 and the member 950 join to form an opening 916extending from the superior surface 942 to the inferior surface 944 ofthe spacer 912.

The first and second spacer portions 972, 974 may be joined together inany suitable manner. For example, the first and second spacer portions972, 974 may be mated together by a splice joint, scarf joint, buttjoint, or the like. The splice joint may include, for example, a halflap splice joint, a bevel lap splice joint, a tabled splice joint, orthe like. In particular, the splice joint may include joining two piecesof material together by at least partially overlapping them (e.g.,overlapping at least a portion of the first spacer portion 972 and atleast a portion of the second spacer portion 974). In the embodimentshown in FIG. 11A, the joint portion between first and second spacerportions 972, 974 is at least partially a half lap splice joint suchthat the joint does not increase the height of the spacer 912. In a halflap splice joint, material is removed from each of the members so thatthe resulting joint is the thickness of the two members as combined.Although not shown, the splice joint between the first and second spacerportions 972, 974 may be beveled or scarfed, stepped, notched, keyed,nibbed, or the like. Any type of joint formed between the first andsecond spacer portions 972, 974 may be further secured with one or morepins 978 or the like.

The member 950 has an upper surface 962, a lower surface 964, a firstlateral portion 966, a second lateral portion 968, and at least one hole934 traversing the member 950 for receiving a fastener, such as a screw930. The upper surface 962 and/or lower surface 964 may extend adistance beyond the superior surface 942, the inferior surface 944, orboth surfaces 942, 944 of the spacer 912. In particular, a portion ofmember 950 may extend above or below the superior and inferior surfaces942, 944 of the spacer 912. The projections of the upper and lowersurfaces 962, 964 may each be in the form of an eyebrow 960. The eyebrow960 may include a rounded portion, for example, with a smooth surface.The upper and lower surfaces 962, 964 may further include one or moretorsional stabilizers 970 configured to prevent or minimize torsionalmotion of the implant 900 once implanted. The torsional stabilizers maybe positioned, for example, substantially medially and laterally alongthe length of the member 950. The torsional stabilizers 970 may includea spiked or pointed projection or extension configured to engageadjacent vertebrae.

The member 950 is coupled to the spacer 912 such that the first end 972a of the first spacer portion 972 engages the first lateral portion 966of the member 950 and the second end 974 b of the second spacer portion974 engages the second lateral portion 968 of the member 950. The spacerportions 972, 974 and the member 950 may also be joined together in anysuitable manner. The member 950 may be configured to mirror the shapeand design of the spacer 912. The spacer 912 may define at least onerecess, projection, etc. sized and dimensioned to retain at least aportion of the member 950. Similar to the insert configurationsdiscussed in this document, member 950 may rest against a portion of thespacer portions 972, 974 or a recess therein to form a joint, such as alap joint, half lap joint, dovetail lap joint, beveled lap joint orscarf joint, stepped lap joint, tabled lap joint, or the like. Inparticular, at least a portion of the member 950 may at least partiallyoverlap at least a portion of the spacer 912 or vice versa. In theembodiment shown in FIG. 11A, the joint portions between the member 950and the spacer 912 are at least partially a half lap joint such that thejoint does not increase the height of the spacer 912.

For example, the member 950 may include a first extension 967 extendingfrom the first lateral portion 966 and a second extension (not visible)extending from the second lateral portion 968. The first extension 967and second extension may extend posteriorly away from a front surface965 of the member 950 and toward the distal end 946 of the spacer 912when attached thereto. The first extension 967 may contact a first ledge973 on the first spacer portion 972 to form a first half lap joint.Similarly, the second extension may contact a second ledge on the secondspacer portion 974 to form a second half lap joint. The extensions 967and ledges 973 may be configured to be complimentary and mate together,for example, with planar surfaces, curved surfaces, tapers, bevels,notches, or the like. Depending on the configuration of the joints, thejoints may form a press-fit or friction-fit engagement to secure themember 950 to the spacer 912 or the joints may be further secured, forexample, with adhesives, pins 978, or the like. For example, the firstand second half lap joints may each be further secured with at least onepin 978.

When present, the pins 978 may traverse at least a portion of the spacer912 and/or the member 950. For example, the extensions 967 may includeone or more openings 980 extending therethrough sized and configured toreceive a portion of pin 978 to secure the member 950 to the spacer 912.Similarly, the corresponding portion of the spacer 912 may include oneor more openings 980 extending therethrough sized and configured toreceive the remainder of pin 978 to secure the member 950 to the spacer912. These openings 980 may or may not be threaded. The pins 978 maypass through holes 980, for example, in a substantially perpendicularmanner relative to a horizontal plane to secure the joints between themember 950 and the spacer 912. For example, the pins 978 may be orientedsubstantially perpendicular relative to the superior and/or inferiorsurfaces 942, 944 of the spacer 912. The pins 978 may be in the form ofdowels (as shown connecting the first spacer portion 972 to the secondspacer portion 974) or may be at least partially threaded (as shownconnecting the member 950 to the spacer 912). The pins 978 may be formedfrom a biocompatible material, such as titanium, or the pins 978 may beformed from tantalum, for example, to enable radiographic visualization.

The implant 900 may also include a locking mechanism 920 disposed on themember 950 for preventing back out of the screws 930. For example, acam-style blocking mechanism may be used with screws 930 that capturethe fixation device screws 930 once they are inserted fully through themember 950. As shown, the anti-back out mechanism 920 may include asingle set screw 932 that retain the screws 930 with the implant 900,although any suitable anti-back out mechanism 920 may be selected by oneof ordinary skill in the art.

FIGS. 12A-12E provide a twelfth embodiment of an implant 1000. Ingeneral, most of the structure of implant 1000 is similar or comparableto the structure of implant 1. In addition, this embodiment issubstantially the same as the implant 900 discussed above, and thediscussion for implant 900 applies equally here with the same referencenumbers provided for unchanged elements. In this particular embodiment,the first and second spacer portions 1072, 1074 are connected togetherby a connector 1084 instead of being attached directly to one another.This allows the first and second spacer 1072, 1074 to be spaced apartwith respect to one another. The connector 1084 may also be formed of amaterial different from the spacer portions 1072, 1074, for example, toallow for strength, support, radiographic visualization, or the like.

The first and second spacer portions 1072, 1074 may be secured togetherwith one or more connectors 1084. The connector 1084 may be sized,shaped, and configured in any suitable manner to join the second end1072 b of the first spacer portion 1072 to the first end 1074 a of thesecond spacer portion 1074. Any of the joints discussed in this documentmay be suitable to join the first and second spacer portions 1072, 1074using connector 1084.

In the embodiment depicted in FIG. 12A, the connector 1084 has asubstantially t-shaped, plus-shaped, or cross-shaped configuration. Forexample, the connector 1084 may include at least first and second tenons1086 sized and configured to be received within mortises 1088 in thespacer portions 1072, 1074. For example, a first tenon 1086 projectinglaterally from the connector 1084 may be size and configured to bereceived within a first mortise 1088 in the second end 1072 b of thefirst spacer portion 1072 and the second tenon 1086 projecting laterallyin the other direction from the connector 1084 may be sized andconfigured to be received with the second mortise 1088 in the first end1074 a of the second spacer portion 1074.

The tenons 1086 may include additional superior and inferiorprojections, for example, which mate with a substantially t-shaped,plus-shaped, or cross-shaped mortise 1088. The mortise and tenonconfiguration may be of any suitable size, shape, and dimension to jointhe connector 1084 to the respective spacer portions 1072, 1074. As inthe other embodiments, the joint may be further secured with one or morepins 1078. In particular, the pins 1078 may be positioned through eachof the tenons 1086 to affix the connector 1084 to the respective spacerportions 1072, 1074. The pins 1078 may be positioned through openings1080 in the tenons 1086 and corresponding openings 1080 in the spacerportions 1072, 1074.

According to a thirteenth embodiment shown in FIGS. 13A-13G, a singlepiece or unitary implant 1100 is provided with an anterior portion 1150and a spacer portion 1112. Certain features of implant 1100 are similaror comparable to the structure of implant 1. In this embodiment, theinserts 50 have been replaced with an anterior portion 1150, and thespacer 1112 and the anterior portion 1150 form a one piece, standalonedesign.

The spacer 1112 has a superior surface 1142, an inferior surface 1144, adistal end 1146, a proximal end 1148, and first and second lateral sides1136, 1138. The superior surface 1142 and the inferior surface 1144 eachhave a contact area 1122 configured to engage adjacent vertebrae. Thecontact areas 1122 may include one or more protrusions 1113 on thesuperior and inferior surfaces 1142, 1144 of each implant 1100 designedto grip the endplates of the adjacent vertebrae, resist migration, andaid in expulsion resistance. The plurality of protrusions 1113 may bepyramidal in shape and may form a series of ridges and grooves (asshown), but the protrusions 1113 can be configured to be any size orshape to enhance anchoring the spacer 1112 and the implant 1100 to eachof the adjacent vertebrae.

The spacer 1112 defines an opening 1116 extending from the superiorsurface 1142 to the inferior surface 1144 of the spacer 1112 configuredto receive bone graft materials. The spacer also defines openings 1117extending through the lateral sides 1136, 1138 and into to the opening1116. These lateral openings 1117 may be in fluid communication with thecentral opening 1116. These openings 1117 may be configured to allow forcompression and expansion of the superior and inferior portions of thespacer 1112.

The distal end 1146 of the spacer 1112 may include a leading taper 1140for ease of insertion into the disc space. The leading taper 1140 may bein the form of a chamfer or a bevel which enables self-distraction ofthe vertebral bodies during insertion of the implant 1100. The leadingtaper 1140 may be located along the insertion direction of the implant100. For example, the leading taper 1140 may assist in an anteriorapproach to the disc space. The distal end 1146 may also include agroove or recess extending between the lateral sides 1136, 1138 tofacilitate compression and expansion of the implant 1100.

The anterior portion 1150 has an upper surface 1162, a lower surface1164, a first lateral portion 1166, a second lateral portion 1168, andat least one hole 1134 traversing the anterior portion 1150 forreceiving a fastener, such as a screw 1130. At least a portion of theupper surface 1162 or the lower surface 1164 of the anterior portion1150 extends beyond the superior surface 1142 or the inferior surface1144 of the spacer 1112. The projections of upper surface 1162 and/orlower surface 1164 may be in the form of an eyebrow 1160. The eyebrow1160 may include a rounded portion having a smooth surface. The uppersurface 1162 and/or lower surface 1164 may further include one or moretorsional stabilizers 1170 configured to prevent or minimize torsionalmotion of the implant 1100 once implanted. The torsional stabilizer 1170may include a spiked or pointed projection or extension, for example,positioned medially and/or laterally on the anterior portion 1150.

The anterior portion 1150 extends from the proximal end 1148 of thespacer 1112 such that the anterior portion 1150 and the spacer 1112 area single piece. As a single, unitary piece the anterior portion 1150 andthe spacer 1112 may be formed from a single piece of material, such astitanium. By way of example as shown in FIGS. 13C and 13D, at least onebeam 1188 may connect the anterior portion 1150 to the proximal end 1148of the spacer 1112 to form a unitary piece. The beam 1118 may extendfrom a substantially medial position to a lateral position of the spacer11112. The beam 1118 may extend across the entire width of the spacer1112 or a portion thereof. The beam 1118 may be interrupted by a gap,for example, positioned substantially medially. No additional fixationdevices or mechanisms are required to attach the anterior portion 1150to the spacer portion 1112, but any suitable fixation systems may beselected by one of ordinary skill in the art.

The spacer 1112 includes one or more spring features 1190, for example,to allow for compression and/or expansion of the implant 1100. Thus, thespacer 1112 has a flexible nature with flexible sections or portions. Inparticular, the spring features 1190 are designed such that the spacer1112 is able to mimic the properties of bone and/or PEEK especially whenimplanted between adjacent vertebrae. For example, the modulus ofelasticity for bone, depending on the type, temperature, strain rate,and other factors, may range from about 0.5-25 GPa. In particular,cancellous bone has a modulus of elasticity of about 0.5-5 GPa. TheYoung's modulus of PEEK is about 3-4 GPa. Thus, PEEK is often used dueto its bone-like modulus of elasticity. A solid block of titanium, onthe other hand, has a much higher modulus of about 100-110 GPa. As areplacement to traditional PEEK implants, implant 1100 is provided withspring-like features 1190 such that the implant 1100, even when formedof titanium, can emulate the modulus of elasticity of cancellous bone.For example, the spacer 1112 may provide for a modulus of elasticity ofabout 0.5-5 GPa, about 1-5 GPa, about 2-5 GPa, or about 3-4 GPa for theimplant 1100.

The spacer 1112 may provide for additional flexibility and an additionalrange of motion with respect to the two adjacent vertebrae. For example,the spacer 1112 may allow for at least two degrees of motion dependingupon the direction and location of the applied force. In particular, theimplant 1100 may allow for forward/anterior or aft/posterior bending andlateral bending to the left or right sides. This type of motion andflexibility may allow for more natural movement of the spinal column.

The spring features 1190 may be of any suitable design or configurationto provide compression and/or expansion of superior and inferiorsurfaces 1142, 1144 of the spacer 1112. For example, the spring feature1190 may be in the form of a cantilevered v-spring having an elongatedsolid spring member with a cross-sectional configuration in the form ofa V. As shown, the distal end 1146 of the spacer 1112 may have a firstspring feature 1190. For example, the first spring feature 1190 may bein the form of a first v-spring. In addition, the proximal end 1148 ofthe spacer 1112 may include a second spring feature 1190. The secondspring feature 1190 may also be in the form of a second v-spring. Thefirst and second spring features 1190 may be the same or different. Thefirst and second spring features 1190 may be configured such that thespacer 1112 simulates the modulus of elasticity of bone even when thespacer 1112 and the anterior portion 1150 are comprised of titanium or atitanium alloy.

As shown in FIG. 13C, the first spring feature 1190 on the distal end1136 may include two longitudinal walls 1191 a, 1191 b provided with anangle therebetween. The angle between the two longitudinal walls 1191 a,1191 b of the v-spring may range from about 45°-170°, about 60°-150°,about 80°-130°, or about 70°-100°, for example. The distal portions ofthe two longitudinal walls 1191 a, 1191 b may be anchored to thesuperior and inferior portions of the spacer 1112 by additional v-springconfigurations. For example, the first longitudinal wall 1191 a mayinterface with the superior portion of the spacer 1112 by a v-spring,which is inverted relative to the v-spring provided between the firstand second longitudinal walls 1191 a, 1191 b. Similarly, the secondlongitudinal wall 1191 b may interface with the inferior portion of thespacer 1112 by another v-spring, which is inverted relative to thev-spring provided between the first and second longitudinal walls 1191a, 1191 b. Thus, the first spring feature 1190 provided on the distalend 1136 may include a zig-zag of three v-springs oriented in oppositedirections. The angle of the v-spring between the first and secondlongitudinal walls 1191 a, 1191 b may be greater than the anglesconnecting the respectively longitudinal walls 1191 a, 1191 b to thesuperior and inferior portions of the spacer 1112.

The implant 1100 may include a second spring feature 1190 on theproximal end 1148 of the spacer 1112. The second spring feature 1190 mayalso include two longitudinal walls 1192 a, 1192 b provided with anangle therebetween. The angle between the two longitudinal walls 1192 a,1192 b of the v-spring may again range from about 45°-170°, about60°-150°, about 80°-130°, or about 70°-100°, for example. This angle maybe the same, larger, or smaller than the angle between the first andsecond longitudinal walls 1191 a, 1191 b at the distal end 1136. Theapex of the angle may form a junction to connect with the beam 1188,which connects the spacer portion 1112 to the anterior portion 1150.

The distal portions of the two longitudinal walls 1192 a, 1192 b may beanchored to the superior and inferior portions of the spacer 1112,respectively by additional v-spring configurations. For example, thefirst longitudinal wall 1192 a may interface with the superior portionof the spacer 1112 by a v-spring, which is inverted relative to thev-spring provided between the first and second longitudinal walls 1192a, 1192 b. Similarly, the second longitudinal wall 1192 b may interfacewith the inferior portion of the spacer 1112 by another v-spring, whichis inverted relative to the v-spring provided between the first andsecond longitudinal walls 1192 a, 1192 b. Thus, the second springfeature 1190 provided on the proximal end 1148 may include a zig-zag ofthree v-springs oriented in opposite directions. The angle of thev-spring between the first and second longitudinal walls 1192 a, 1192 bmay be the same or greater than the angles connecting the respectivelylongitudinal walls 1192 a, 1192 b to the superior and inferior portionsof the spacer 1112. Additional recesses 1194 may be provided on thesuperior and inferior portions of the spacer 1112 to allow for propermovement of the v-springs. In particular, the recesses 1194 may beformed such that the apexes of the upper and lower v-portions arerevealed. As shown in FIG. 13C, the recesses 1194 may be rounded orcurved. In an alternative embodiment shown in FIG. 13G, the recesses1194 may be angled or pointed.

Although a v-shaped spring is exemplified in this embodiment, the springportions 1190 may be formed in any suitable shape or configuration notlimited to the v-shape, and may include, for example, U-shape, S-shape,coiled, square, rectangular, sinusoidal, corrugated and accordionpleated. In addition, the shape of the spring features 1190 may besymmetrical or non-symmetrical. For example, the longitudinal walls 1191a, 1191 b, 1192 a, 1192 b may be symmetrical or non-symmetrical withrespect to one another.

According to a fourteenth embodiment shown in FIG. 14, which may beparticularly suitable for an anterior cervical procedure, an implant1200 including a frame 1250 with one or more endplates 1212 is provided.FIG. 14 depicts an exploded view of the implant 1200. The frame 1250 maybe substantially in the form of a split-ring or partial loop of materialwith a central opening. When combined with the endplates 1212, which maybe shaped and configured to match the central opening in the frame 1250,the opening may provide for a graft opening area configured to providethe maximum amount of volume for bone graft packing. The graft area maybe configured for receiving bone graft material, for example, to promotefusion of the adjacent vertebral bodies.

The frame 1250 may include a front portion 1265. The front portion 1265may define one or more fastener apertures 1234 configured to securefasteners, such as bone screws (not shown), in both the superior andinferior vertebrae. The front portion 1265 may be a unitary piece or maybe divided into two separate portions with a passage or gap 1224positioned therebetween. The front portion 1265 may include an uppersurface 1262 and a lower surface 1264. A first arm 1254 may extend froma first end of the front portion 1265 and a second arm 1254 may extendfrom a second end of the front portion 1265 of the frame 1250. The arms1254 may join together to form the full or partial ring-like structure.The frame 1250 may also include a rear portion 1255. The arms 1254 maymeet at the rear portion 1255 of the frame 1250, for example. The frontportion 1265 may have a height greater than the height of the arms 1250and the rear portion 1255.

One or more endplates 1212 are positioned on and affixed to the frame1250 such that at least a portion of the ring portion of the frame 1250is covered or housed within the endplates 1212. Preferably, the frontportion 1265 of the frame 1250 is not covered by the endplates 1212. Theendplates 1212 may form a superior surface 1242 and an inferior surface1244 configured to contact and engage adjacent vertebrae (not shown).The superior and inferior surfaces 1242, 1244 may be parallel, curved,or angled to help restore or recreate a lordosis angle (or other angle)of the human spine. In addition, the superior and/or inferior surfaces1242, 1244 may be contoured to conform more closely to the concaveendplates of the adjacent vertebra.

In order to engage the adjacent vertebrae, the endplates 1212 mayinclude a plurality of protrusions 1213 or teeth on the contact areas ofthe superior and/or inferior surfaces 1242, 1244. The protrusions 1213may help to grip the endplates of the adjacent vertebrae, resistmigration, and aid in expulsion resistance. The plurality of protrusions1213 may be pyramidal in shape, but the protrusions 1213 can beconfigured to be any size or shape to enhance anchoring of the implant1200 to each of the adjacent vertebrae.

As shown in FIG. 14, two endplates 1212 may be provided. A firstendplate 1212 may have a substantially c-shaped configuration designedto follow the shape of the rear portion 1255 of the frame 1350. Theendplate 1212 may include a recess or channel 1223 designed andconfigured to retain at least a portion of the ring and, in particular,at least the rear portion 1255 and a portion of the arms 1254 of theframe 1250. This endplate 1212 may also include a leading taperconfigured to ease insertion of the implant 1200 into the disc space.

A second endplate 1212 may be provided to at least partially residewithin the passage or gap 1224 in the front portion 1265 of the frame1250. In particular, this endplate 1212 may include a central portion1235 sized and configured to fit within the gap 1224. The centralportion 1235 may form a portion of the superior surface 1242 (e.g.,having protrusions 1213 extending superiorly) and a portion of theinferior surface 1244 (e.g., having protrusions 1213 extendinginferiorly). In addition, the central portion 1235 may include anopening sized and configured to receive an insert 1252 which accepts ananti-backout locking mechanism 1220. The locking mechanism 1220 may beprovided to block or unblock the heads of the fasteners or screws whenpositioned within the respective fastener apertures 1234. The anti-backout mechanism 1220 may include, for example, a set screw configured toblock a portion of the fasteners positioned through the frame 1250.

In addition to the central portion 1235, the endplate 1212 may alsoinclude a first lateral wing 1236 and a second lateral wing 1238. Thefirst lateral wing 1236 may be configured to contact a first side of oneof the arms 1254 and the second lateral wing 1238 may be configured tocontact a second side of the other arm 1254. In this manner, theendplate 1212 may be positioned such that the first lateral wing 1236forms a portion of the superior surface 1242 (e.g., having protrusions1213 extending superiorly) and the second lateral wing 1238 forms aportion of the inferior surface 1244 (e.g., having protrusions 1213extending inferiorly). It is envisioned that the positions of the wings1236, 1238 may be changed or reversed as one of ordinary skill in theart may recognize.

One or more of the endplates 1212 may be secured to the frame 1250 usingany of the mechanisms or techniques described herein. In particular, oneor more of the endplates 1212 may be secured with one or more pins 1278.Any suitable number, type, and location for the pins 1278 may beselected. For example, two pins 1278 may be positioned within openingslocated adjacent to and on opposite sides of the front portion 1265 ofthe frame 1250.

In this embodiment, the frame 1250 provides two fastener apertures 1234to secure fasteners, such as bone screws, in both the superior andinferior vertebrae. For example, the fastener apertures 1234 may extendthrough the front portion 1265 of the frame 1250 at an angle. A portionof the upper and/or lower surfaces 1262, 1264 of the frame 1250 mayextend a distance beyond the superior surface 1242, the inferior surface1244, or both surfaces 1242, 1244 of the endplates 1212. The projectionsof the upper and lower surfaces 1262, 1264 of the frame 1250 may be inthe form of eyebrows 1260. In this embodiment, the eyebrows 1260 includea substantially smooth and curved surface. One or more torsionalstabilizers 1270 may also be provided and configured to prevent orminimize torsional motion of the implant 1200 once implanted. Thetorsional stabilizers 1270 may include a spiked or pointed projection orextension configured to engage adjacent vertebrae.

According to a fifteenth embodiment shown in FIGS. 15A and 15B, whichmay be particularly suitable for an anterior lumbar procedure, implants1300 a, 1300 b include a frame 1350 a, 1350 b with one or more endplates1312 a, 1312 b. FIGS. 15A and 15B depict exploded views of the implants1300 a, 1300 b. The frames 1350 a, 1350 b may be substantially in theform of a ring or loop of material with a central opening divided intotwo equal halves. The endplates 1312 a, 1312 b, for example, in the formof PEEK or allograft spacers, may be sized and configured to fit withinthe openings.

The frames 1350 a, 1350 b may each include a front portion 1365 a, 1365b, which defines one or more fastener apertures 1334 a, 1334 bconfigured to secure fasteners, such as bone screws (not shown), in boththe superior and inferior vertebrae. The front portion 1365 a, 1365 bmay extend from a first lateral end to a second lateral end of the frame1350 a, 1350 b. A first arm 1354 a, 1354 b may extend from a first endof the front portion 1365 a, 1365 b and a second arm 1354 a, 1354 b mayextend from a second end of the front portion 1365 a, 1365 b of theframe 1350 a, 1350 b. The arms 1354 a, 1354 b may join together to formthe ring-like structure of the frame 1350 a, 1350 b. The frame 1350 a,1350 b may include a rear portion 1355 a, 1355 b where the arms 1354 a,1354 b connect together.

In this embodiment, the frame 1350 a, 1350 b provides three fastenerapertures 1334 a, 1334 b to secure fasteners, such as bone screws, inboth the superior and inferior vertebrae. For example, the fastenerapertures 1334 a, 1334 b may extend through the front portion 1365 a,1365 b of the frame 1350 a, 1350 b at an angle. As described herein,once inserted through the fastener apertures 1334 a, 1334 b, thefasteners may be secured with an anti-back out prevention or lockingmechanism 1320 a, 1320 b, such as by using one or more blocking screw tocapture a portion of the fasteners to prevent back out.

The frame 1350 a, 1350 b may also include a support member 1356 a, 1356b. The support member 1356 a, 1356 b may divide or segment the centralopening and provide stability to the frame 1350 a, 1350 b. As shown, thesupport member 1356 a, 1356 b may be a medial portion of the implant1300 a, 1300 b, which is positioned centrally to divide the centralopening into two equal halves. It is envisioned, however, that thesupport member 1356 a, 1356 b may be absent creating a single largeopening, the support member 1356 a, 1356 b may be offset such that thetwo openings are not equal in size, or more than one support member 1356a, 1356 b may be provided to create multiple openings for the endplates1312 a, 1312 b to reside. The support member 1356 a, 1356 b may alsohave at least one opening 1358 a, 1358 b extending therethrough toretain a corresponding protrusion 1314 a, 1314 b on the endplates 1312a, 1312 b. The opening 1358 a, 1358 b in the support member 1356 a, 1356b may be elongated with a curved or beveled perimeter designed toprovide an interference fit when the endplate 1312 a, 1312 b is snappedinto the openings of the frame 1350 a, 1350 b. Although a single opening1358 a, 1358 b in the support member 1356 a, 1356 b is shown, additionalopenings may also be provided to secure the endplates 1312 a, 1312 b. Inaddition or alternatively, similar openings may be provided in the arms1354 a, 1354 b of the frame 1350 a, 1350 b to secure the endplates 1312a, 1312 b. The front portion 1365 a, 1365 b may have a height greaterthan the height of the arms 1354 a, 1354 b and/or the rear portion 1355a, 1355 b. In addition, the support member 1356 a, 1356 b may have aheight greater than the height of the arms 1354 a, 1354 b.

One or more endplates 1312 a, 1312 b are positioned on and affixed tothe frame 1350 a, 1350 b such that at least a portion of the endplates1312 a, 1312 b is received within the openings in the frame 1350 a, 1350b. The endplates 1312 a, 1312 b may be inserted from the top or thebottom of the implant 1300 a, 1330 b. The endplates 1312 a, 1312 b mayinclude upper and lower surfaces configured to contact and engageadjacent vertebrae (not shown). The upper and lower surfaces may beparallel, curved, or angled to help restore or recreate a lordosis angle(or other angle) of the human spine. In addition, the upper and/or lowersurfaces may be contoured to conform more closely to the concaveendplates of the adjacent vertebra.

The endplates 1312 a, 1312 b may be L-shaped with a steppedconfiguration, for example, or may include a raised portion sized andconfigured to fit within the central opening of the frame 1350 a, 1350b. For example, the raised portion may form a portion of the upperand/or lower surfaces. This configuration may allow for the endplates1312 a, 1312 b to bottom out on the frame 1350 a, 1350 b preventingexcessive force from pushing the endplates 1312 a, 1312 b out the otherend of the implant 1300 a, 1300 b upon insertion. The endplates 1312 a,1312 b may include a plurality of protrusions 1313 a, 1313 b or teeth onthe contact areas of the upper and/or lower surfaces to engage theadjacent vertebrae. The protrusions 1313 a, 1313 b may help to grip theendplates of the adjacent vertebrae, resist migration, and aid inexpulsion resistance. The plurality of protrusions 1313 a, 1313 b may bepyramidal in shape and may form a series of ridges and grooves (asshown), but the protrusions 1313 a, 1313 b can be configured to be anysize or shape to enhance anchoring the implant 1300 a, 1300 b to each ofthe adjacent vertebrae.

As shown in FIGS. 15A and 15B, two endplates 1312 a, 1312 b may beprovided for each implant 1300 a, 1300 b. The endplates 1312 a, 1312 bfor each respective implant 1300 a, 1300 b may be mirror images of oneanother. The endplates 1312 a, 1312 b may include a lateral surfacehaving at least one protrusion 1314 a, 1314 b extending outwardlytherefrom. The edges of the protrusion 1314 a, 1314 b may be chamferedor beveled such that the protrusion 1314 a, 1314 b provides aninterference fit with the opening 1358 a, 1358 b in the support member1356 a, 1356 b. Although depicted with the protrusions 1314 a, 1314 b,the endplates 1312 a, 1312 b may be secured to the frame 1350 a, 1350 busing any of the mechanisms or techniques described herein.

A sixteenth embodiment is shown in FIGS. 16A and 16B, which depictexploded views of implants 1400 a, 1400 b. This embodiment issubstantially the same as the implants 1300 a, 1300 b discussed above,and the discussion for implants 1300 a, 1300 b applies equally here. Inthis particular embodiment, implants 1400 a, 1400 b include a frame 1450a, 1450 b with one or more endplates 1412 a, 1412 b. Instead of forminga ring or loop, the frame 1450 a, 1450 b includes extensions or arms1454 a, 1454 b and support member 1456 a, 1456 b to secure the endplates1412 a, 1412 b. The endplates 1412 a, 1412 b may be in the form of PEEKor allograft spacers, for example, sized and configured to fit withinthe openings or channels defined between the arms 1454 a, 1454 b andsupport member 1456 a, 1456 b.

The front portion 1465 a, 1465 b of the frame 1450 a, 1450 b defines oneor more fastener apertures 1434 a, 1434 b configured to securefasteners, such as bone screws (not shown), in both the superior andinferior vertebrae. In this embodiment, the frame 1450 a, 1450 bprovides three fastener apertures 1434 a, 1434 b extending through thefront portion 1465 a, 1465 b of the frame 1450 a, 1450 b at an angle tosecure fasteners, such as bone screws, in both the superior and inferiorvertebrae. As described herein, once inserted through the fastenerapertures 1434 a, 1434 b, the fasteners may be secured with an anti-backout prevention or locking mechanism 1420 a, 1420 b, such as by using oneor more blocking screw to capture a portion of the fasteners to preventback out.

The frame 1450 a, 1450 b may include a first arm 1454 a, 1454 bextending from a first end of the front portion 1465 a, 1465 b and asecond arm 1454 a, 1454 b extending from a second end of the frontportion 1465 a, 1465 b. A support member 1456 a, 1456 b may bepositioned between the arms 1454 a, 1454 b. As shown, the support member1456 a, 1456 b may be positioned at a medial portion of the implant 1400a, 1400 b, and may be positioned centrally between the arms 1454 a, 1454b. It is envisioned, however, that the support member 1456 a, 1456 b maybe absent creating a single large opening, the support member 1456 a,1456 b may be offset creating unequally sized openings, or more than onesupport member 1456 a, 1456 b may be provided to create multiplelocations for the endplates 1412 a, 1412 b to reside.

The support member 1456 a, 1456 b may also have at least one opening1458 a, 1458 b extending therethrough to retain a correspondingprotrusion 1414 b (protrusion not visible in FIG. 16A) on the endplates1412 a, 1412 b. The opening 1458 a, 1458 b in the support member 1456 a,1456 b may be elongated with a curved or beveled perimeter designed toprovide an interference fit when the endplate 1412 a, 1412 b is snappedinto openings or channels between the arms 1454 a, 1454 b and supportmember 1456 a, 1456 b. Although a single opening 1458 a, 1458 b in thesupport member 1456 a, 1456 b is shown, additional openings may also beprovided to secure the endplates 1412 a, 1412 b. In addition oralternatively, similar openings may be provided in the arms 1454 a, 1454b of the frame 1450 a, 1450 b to secure the endplates 1412 a, 1412 b.

One or more endplates 1412 a, 1412 b are configured to be positioned onand/or affixed within openings or channels between the arms 1454 a, 1454b and support member 1456 a, 1456 b. The endplates 1412 a, 1412 b may beinserted from the top, bottom, or back of the implant 1400 a, 1400 b.The endplates 1412 a, 1412 b may include upper and lower surfacesconfigured to contact and engage adjacent vertebrae (not shown). Theupper and lower surfaces may be parallel, curved, or angled to helprestore or recreate a lordosis angle (or other angle) of the humanspine. In addition, the upper and/or lower surfaces may be contoured toconform more closely to the concave endplates of the adjacent vertebra.

The endplates 1412 a, 1412 b may be notched or provided with a steppedconfiguration or may include a raised portion sized and configured tofit between the arms 1454 a, 1454 b and support member 1456 a, 1456 b.This configuration may allow for the endplates 1412 a, 1412 b to bottomout on the frame 1450 a, 1450 b preventing excessive force from pushingthe endplates 1412 a, 1412 b out the other end upon insertion. Theendplates 1412 a, 1412 b may include protrusions 1413 a, 1413 b or teethon the contact areas of the implant 1400 a, 1400 b as discussed herein.

As shown in FIGS. 16A and 16B, two endplates 1412 a, 1412 b may beprovided for each implant 1400 a, 1400 b. The endplates 1412 a, 1412 bfor each respective implant 1400 a, 1400 b may be mirror images of oneanother. The endplates 1412 b may include a lateral surface having atleast one protrusion 1414 b extending outwardly therefrom. Similarprotrusions are provided on endplates 1412 a in FIG. 16A, which are notvisible in the view provided. The edges of the protrusion 1414 b may bechamfered or beveled to provide an interference fit with the opening1458 b in the support member 1456 b. Although shown to be secured withthe protrusions 1414 b, the endplates 1412 a, 1412 b may be additionallyor alternatively secured to the frame 1450 a, 1450 b using any of themechanisms or techniques described herein.

As shown in FIGS. 17A and 17B, a seventeenth embodiment includesexploded views of implants 1500 a, 1500 b. This embodiment issubstantially the same as the implants 1400 a, 1400 b discussed above,and the discussion for implants 1400 a, 1400 b applies equally here.Implants 1500 a, 1500 b include a frame 1550 a, 1550 b with one or moreendplates 1512 a, 1512 b configured to be positioned between theextensions or arms 1554 a, 1554 b and support member 1556 a, 1556 b tosecure the endplates 1512 a, 1512 b. This embodiment includesprotrusions 1514 a, 1514 b on the medial portion of the endplate 1512 a,1512 b as well as indentations 1516 a, 1516 b on the lateral portion ofthe endplate 1512, 1512 b to provide an interference fit with the frame1550 a, 1550 b. The endplates 1512 a, 1512 b may be in the form of PEEKor allograft spacers, for example, sized and configured to fit withinthe openings or channels between the arms 1554 a, 1554 b and supportmember 1556 a, 1556 b.

The frame 1550 a, 1550 b may include a first arm 1554 a, 1554 bextending from a first end of the front portion 1565 a, 1565 b and asecond arm 1554 a, 1554 b extending from a second end of the frontportion 1565 a, 1565 b. The support member 1556 a, 1556 b may bepositioned between the arms 1554 a, 1554 b, for example, at a centrallocation between the arms 1554 a, 1554 b. The support member 1556 a,1556 b may have at least one opening 1558 a, 1558 b extendingtherethrough to retain a corresponding protrusion 1514 a, 1514 b on themedial portion of the endplates 1512 a, 1512 b. The opening 1558 a, 1558b in the support member 1556 a, 1556 b may be elongated with a curved orbeveled perimeter designed to provide an interference fit when theendplate 1512 a, 1512 b is snapped into openings or channels between thearms 1554 a, 1554 b and support member 1556 a, 1556 b. The lateralportion of the endplates 1512 a, 1512 b may include at least oneindentation 1516 a, 1516 b therein to retain a corresponding protrusion1518 a, 1518 b on an interior surface of the arms 1554 a, 1554 b. Theindentation 1516 a, 1516 b in the endplates 1512 a, 1512 b may besubstantially square with a curved or beveled perimeter designed toprovide an interference fit when the endplate 1512 a, 1512 b is snappedinto openings or channels between the arms 1554 a, 1554 b and supportmember 1556 a, 1556 b. The protrusions 1514 a, 1514 b on the endplates1512 a, 1512 b may be larger in size and shape than the protrusions 1518a 1518 b on the arms 1554 a, 1554 b, for example. Although it isenvisioned that any size, shape, dimension, and position for theprotrusions 1514 a, 1514 b, 1518 a, 1518 b may be selected by one ofordinary skill in the art.

The endplates 1512 a, 1512 b may be notched and contoured to fit betweenthe arms 1554 a, 1554 b and support member 1556 a, 1556 b. As shown inFIGS. 17A and 17B, two endplates 1512 a, 1512 b may be provided for eachimplant 1500 a, 1500 b. The endplates 1512 a, 1512 b for each respectiveimplant 1500 a, 1500 b may be mirror images of one another. Theendplates 1512 a, 1512 b may be inserted from the top, bottom, or backof the implant 1500 a, 1500 b. The endplates 1512 a, 1512 b may includeupper and lower surfaces configured to contact and engage adjacentvertebrae (not shown). The upper and lower surfaces may be parallel,curved, angled, contoured, or the like to conform more closely with theendplates of the adjacent vertebra.

FIGS. 18A and 18B illustrate stand-alone intervertebral implants 1600 a,1600 b, which may be suitable for an anterior lumbar procedure. Theimplants 1600 a, 1600 b include a spacer or frame 1650 a, 1650 b and oneor more endplates 1612 a, 1612 b. The endplates 1612 a, 1612 b may be inthe form of PEEK or allograft spacers, for example, sized and configuredto fit within the openings in the frame 1650 a, 1650 b.

The frame 1650 a, 1650 b includes upper and lower surfaces each havingcontact areas (e.g., a plurality of protrusions 1613 a, 1613 b)configured to contact and engage adjacent vertebrae (not shown). Theframe 1650 a, 1650 b may contain one or more openings which extend fromthe upper surface to the lower surface. The openings may be in the formof oval holes, for example. As shown, three openings may be provided:two posterior openings and one anterior opening. The openings may beconfigured for receiving bone graft material, for example, to promotefusion of the adjacent vertebral bodies.

In one embodiment, the openings may be configured to receivecorresponding endplates 1612 a, 1612 b. The endplates 1612 a, 1612 b maybe inserted from the top or the bottom of the implant 1600 a, 1600 b.The endplates 1612 a, 1612 b may be retained in the openings by a ridge1614 a, 1614 b and corresponding slot or groove 1616 a, 1616 b locatedon a mid-transverse plane on the implants 1600 a, 1600 b. The ridge 1614a, 1614 b may project around a perimeter of each endplate 1612 a, 1612b. The ridge 1614 a, 1614 b may be centrally located between the upperand lower surface of the implant 1600 a, 1600 b, but is also envisionedthat additional ridges may be provided or the ridge may be offset fromthe center line.

The endplate 1612 a, 1612 b upon insertion has an interference fit andthen snaps into the corresponding groove 1616 a, 1616 b on the frame1650 a, 1650 b. The endplates 1612 a, 1612 may be in the shape of ovalsalthough any suitable shape is envisioned. The posterior ovals aresubstantially the same and are interchangeable. The anterior oval has adistinct feature on its bottom; namely, a slot for the fastener, todistinguish it from the posterior ovals. The endplates 1612 a, 1612 bmay also include protrusions on the upper and/or lower surfaces whichmatch and align with the protrusions 1613 a, 1613 b on the frame 1650 a,1650 b.

The inserts, members, frames, spacers, and endplates described in thisdocument may be comprised of any suitable materials. The spacers orendplates can be comprised of any material that is conducive to theenhancement of fusion between the two adjacent vertebrae. In oneparticular embodiment, the spacer or endplate is made of a biocompatibleplastic, like polyether ether ketone (PEEK), polyetherketoneketone(PEKK), ultra-high molecular weight (UHMW) polyethylene, or otherpolymers and plastics known in the art which are physiologicallycompatible. Any other materials that are physiologically compatible mayalso be used such as bone or metal. The inserts, members, or frames canalso be comprised of any physiologically compatible materials. In thepreferred embodiment, the inserts, members, or frames are composed of abiocompatible metal, such as stainless steel, titanium, titanium alloys,surgical steel, and metal alloys, for example. Preferably, the inserts,members, or frames are formed from titanium or a titanium alloy. Anyother materials that are physiologically compatible may also be usedsuch as bone or plastic.

Although the invention has been described in detail and with referenceto specific embodiments, it will be apparent to one skilled in the artthat various changes and modifications can be made without departingfrom the spirit and scope of the invention. Thus, it is intended thatthe invention covers the modifications and variations of this inventionprovided they come within the scope of the appended claims and theirequivalents. It is expressly intended, for example, that all rangesbroadly recited in this document include within their scope all narrowerranges which fall within the broader ranges. It is also intended thatthe components of the various devices disclosed above may be combined ormodified in any suitable configuration.

What is claimed is:
 1. An intervertebral implant for implantation in anintervertebral space between adjacent vertebrae, the implant comprising:a frame comprising a body, a first extension extending from the body,and a second extension extending from the body, wherein the framefurther comprises a first hole for receiving a first screw and a secondhole for receiving a second screw; a first screw extending through thefirst hole; a second screw extending through the second hole; and aspacer connected to the frame, wherein the spacer comprises a firstspacer portion, a second spacer portion, and a connector between thefirst spacer portion and the second spacer portion, wherein theconnector separates the first spacer portion and the second spacerportion such that they are not in direct contact with one another. 2.The implant of claim 1, wherein the frame further comprises an uppersurface and a lower surface, wherein a first torsional stabilizerextends from the upper surface and a second torsional stabilizer extendsfrom the lower surface.
 3. The implant of claim 1, wherein the framefurther comprises a first eyebrow that forms the first hole and a secondeyebrow that forms the second hole.
 4. The implant of claim 1, whereinthe first screw is angled in an upward direction and the second screw isangled in a downward direction.
 5. The implant of claim 1, wherein theconnector comprises a cross-shaped member.
 6. The implant of claim 1,wherein the connector comprises a first tenon and a second tenon.
 7. Theimplant of claim 6, wherein the first spacer portion comprises a firstmortise for receiving the first tenon and the second spacer portioncomprises a second mortise for receiving the second tenon.
 8. Theimplant of claim 1, wherein the first spacer portion further comprises acut-out portion for receiving a pin therethrough.
 9. The implant ofclaim 8, wherein the pin extends through the connector and the firstspacer portion.
 10. The implant of claim 1, wherein the frame furthercomprises a pair of torsional stabilizers extending from an uppersurface thereof.
 11. An intervertebral implant for implantation in anintervertebral space between adjacent vertebrae, the implant comprising:a frame comprising a body, a first extension extending from the body,and a second extension extending from the body, wherein the framefurther comprises a first hole for receiving a first screw and a secondhole for receiving a second screw; a first screw extending through thefirst hole; a second screw extending through the second hole; and aspacer connected to the frame, wherein the spacer comprises a firstspacer portion, a second spacer portion, and a connector between thefirst spacer portion and the second spacer portion, wherein each of thefirst spacer portion, second spacer portion and connector includes aprotrusion from an upper surface thereof for gripping into bone.
 12. Theimplant of claim 11, wherein the frame further comprises an uppersurface and a lower surface, wherein a first torsional stabilizerextends from the upper surface and a second torsional stabilizer extendsfrom the lower surface, wherein each of the first torsional stabilizerand second torsional stabilizer comprises a triangular cross-section.13. The implant of claim 11, wherein the frame further comprises a firsteyebrow that forms the first hole and a second eyebrow that forms thesecond hole.
 14. The implant of claim 11, wherein the first screw isangled in an upward direction and the second screw is angled in adownward direction.
 15. The implant of claim 11, wherein the connectorcomprises a cross-shaped member.
 16. The implant of claim 11, whereinthe connector comprises a first tenon and a second tenon.
 17. Theimplant of claim 16, wherein the first spacer portion comprises a firstmortise for receiving the first tenon and the second spacer portioncomprises a second mortise for receiving the second tenon.
 18. Theimplant of claim 11, wherein the first spacer portion further comprisesa cut-out portion, wherein the first extension of the frame is receivedin the cut-out portion of the spacer.
 19. The implant of claim 11,wherein the first spacer portion further comprises a first cut-outportion and the second spacer portion further comprises a second cut-outportion.
 20. The implant of claim 19, wherein the first cut-out portionis formed on an upper portion of the first spacer portion and the secondcut-out portion is formed on a lower portion of the second spacerportion.